Natural Solar Radiation Research Articles

Latitude-dependent implications of lighting regimes on lettuce physiology and resource utilisation in decoupled aquaponics systems

Aquaponics, a circular agri-aquaculture system, offers the potential to enhance food production resilience across diverse environmental contexts. Plant physiological processes that regulate water and nutrient fluxes in decoupled aquaponics are responsive to environmental dynamics such as stomatal behaviour. In greenhouses, these dynamics are largely driven by changes in natural solar radiation. This research investigates plant physiological dynamics of lettuce traits to various natural light conditions in a fully climate-controlled environment mimicking geographic latitude-based light variations and lighting application modes. We explored the physiological and resource utilisation effects of these regimes as basis for a geographic-adjusted planning of climate-resilient aquaponic systems. For that, four lighting scenarios were applied in a climate chamber over a period of 21 days in decoupled aquaponic setups, involving two daily light integrals (DLIs) and two daily light dynamics (DLDs) for lighting application modes: North (LAT 59° 54' 41.37'' N) natural sunlight dynamics, North static, South (LAT 40° 25' 0.39'' N) natural sunlight dynamics (Sn), and South static (Ss). DLIs and natural sunlight dynamics were derived from Northern (Oslo, Norway) and Southern (Madrid, Spain) Europe in March 2022. Observed plant physiological variables were plant growth, chlorophyll and carotenoid contents, stomatal conductance and morphology, and net photosynthesis (Pn). Resource-use variables at leaf level, including CO2, light, water, and nutrient utilisation, were also estimated. Latitude-dependent DLIs, in general, significantly affected lettuce growth, quality, and physiological responses; with lower latitudes (Sn, Ss) improving Pn by 68% compared to North-DLI treatments. Resource utilisation was also positively impacted in South-DLI treatments, e.g., light use efficiency was in average 2.2 times higher in South-DLI (0.75 g [CO2] mol−1 [PPFD]) than in North-DLI (1.62 g [CO2] mol−1 [PPFD]) treatments. Lighting modes had limited effects, and interactions between DLIs and DLDs were largely absent. These findings indicate the significance of geographic differences in natural solar radiation dynamics on designing climate-resilient aquaponics facilities, and highlight the influence of geography on crop productivity and resource efficiency.

An Innovative Sunlight‐Driven Device for Photocatalytic Drugs Degradation: from laboratory‐ to real‐Scale Application. A First Step Toward Vulnerable Communities

AbstractFreshwater represents one of the most precious resources on the planet, so it is fundamental to preserve it. In this work, an innovative sunlight‐driven device composed of bismuth oxybromide (BiOBr) grown on a material derived from natural sources, i.e., Lightweight Expanded Clay Aggregates (LECA), is developed to clean surface waters under natural solar light irradiation. For this purpose, the photodegradation of two non‐steroidal anti‐inflammatory drugs, ibuprofen, and diclofenac, is investigated under varying operative conditions. Laboratory‐ and real‐scale experiments reveal that the fabricated floating BiOBr/LECA photocatalyst fully degrades diclofenac, whereas limited abatement of ibuprofen is observed. Based on the identification of specific transformation products (TPs) during the degradation, this behavior seems to be strongly related to the different structures of the two drugs. In fact, the main TP produced during diclofenac degradation derives from dechlorination and ring condensation: this type of photocatalytic degradation pathway is generally favored over the C─C bonds's cleavage, which is a unique possibility for IBU abatement. Moreover, the potential partial adsorption of these species on the photocatalyst's active sites can cause their deactivation. Finally, reusability tests demonstrate the high stability of the floating composite.

Synthesis of Cerium-Doped Zinc Oxide Nanocomposites and Their Application for Photocatalytic Degradation of Lambda-Cyhalothrin in Agricultural Runoff Under Natural Solar Irradiation

Heterogenous photocatalysis is one of the promising methods of degradation of organic pollutants in the environment. This study developed a suitable and efficient method for photocatalytic degradation of Lambda-cyhalothrin LCY pesticide using Ce–ZnO nanocomposites under natural solar irradiation. Ce–ZnO was synthesized using the coprecipitation method and was ascertained through structural characterization. The crystal structure and crystallite size, surface morphology, functional groups present, and the elemental composition of the synthesized nanocomposites were determined by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDAX), respectively. The average crystallite size of the nanocomposites was found to be 31.42 nm. The photocatalytic degradation of LCY was conducted in batches to obtain and determine the optimal conditions for the degradation of the pesticide. It was found that at optimum conditions; 100 ppm LCY initial concentration, 20 mg dose of the photocatalyst, and 10–11 UV index, Ce–ZnO were found to degrade about 92% of the initial concentration of LCY after 3 h of exposure to solar irradiation. It was found that Ce–ZnO possesses high photocatalytic activity against LCY and the kinetic of the degradation was found to fit the pseudo-first-order kinetic model.

Comprehensive Morphometric and Biochemical Characterization of Seven Basil (Ocimum basilicum L.) Genotypes: Focus on Light Use Efficiency

The choice of basil (Ocimum basilicum L.) genotypes determines key attributes such as yield, flavor, and adaptability, contributing significantly to the overall success and sustainability of basil cultivation practices. As the primary aim of this study, seven basil accessions were characterized for both their growth performance and biochemical profile of volatile compounds, enabling the differentiation among distinct chemotypes. As secondary objectives, growth performance and production were evaluated under natural solar radiation conditions (SR100) and with a 30% reduction in solar radiation using a net (SR70). Light use efficiency (LUE) determination revealed the plants’ biomass production capability under different solar radiation (SR) conditions. Genotypes A, B, C, and G were characterized by a high levels of linalool, which is typically associated with the “pesto” sauce smell. Lemon basil D exhibited a different chemotype due to the presence of neral and geranial. E and F displayed a different chemotype due to the higher concentration of α-bergamotene. The total fresh harvested biomass was significantly higher in SR70 than SR100 conditions. The second harvest in both SR conditions was the most productive one, while genotype E under SR70 displayed the highest yield. The landraces D and E showed the highest LUE values, indicating their capability in converting the solar radiation into fresh biomass. Plants grown in SR70 conditions registered significantly higher values of plant height, number of branches, and leaf weight. This work aimed to provide valuable insights into the selection of basil genotypes suitable for sustainable agriculture. Conversely, it lays the basis for cultivation aspects pertaining to the crop’s adaptability in peri-urban, marginal lands, which are characterized by limited solar radiation.

Evaluation of photocatalytic activity of Cu3(PO4)2/MgO nanocomposite for the efficient removal of amaranth dye under solar light irradiation

The amaranth dye was removed using photocatalysis on a Cu3(PO4)2/MgO nanocomposite synthesized by co-precipitation method. The crystalline component and the nanostructure of the samples were analyzed by XRD, FTIR, UV–vis-DRS, SEM, EDS, HR-TEM and EIS confirming the successful formation of the nanocomposite. In powder XRD, the average crystallite size is found to be ∼ 26–37 nm. Electrochemical impedance spectroscopy, Nyquist plots represents the charge-transfer resistance at contact interface and the arc diameter of Cu3(PO4)2/MgO is much smaller than that of pure MgO and Thermo gravimetric analysis (TGA), from TGA curve the weight-loss of Cu3(PO4)2 and Cu3(PO4)2/MgO nanocomposite was calculated as 14.18 % and 18.16 % which gives the more contribution to the large enhancement of photocatalytic activity. The photocatalytic degradation efficiency of Cu3(PO4)2/MgO nanocomposite (0.1 g/L, 10 μM and 150 min) was investigated under natural direct solar light irradiation against the dyes. The rate of degradation of amaranth with Cu3(PO4)2/MgO followed pseudo–first order kinetics in the dye concentration. Degradation efficiency (99 %) and degradation rates of amaranth were increases with increasing Cu3(PO4)2/MgO concentration. Generally, this research work advances the possible utilization of Cu3(PO4)2/MgO as an efficient catalyst for taking away of dye from aqueous solution and improvement the catalyst to be used for a numerous cycles. The Cu3(PO4)2/MgO nanocomposites showed good activity against bacteria of Staphylococcus aureus, Staphylococcus pyogenes and Klebsilla pneumoniae.

Orange peel biochar/clay/titania composites: low cost, high performance, and easy-to-reuse photocatalysts for the degradation of tetracycline in water

New orange peel biochar/clay/titania nanocomposites (NCs) were studied for photocatalytic tetracycline (TET) degradation under both UV and natural solar irradiation by variation of NC dose, initial TET concentration, ionic strength,...

Enhanced performance of dual-functional ZIF-8/red phosphorus photocatalysts for concurrent degradation of organic dyes and hydrogen generation under natural solar light irradiation.

Herein, zeolitic imidazole framework (ZIF)-8/red phosphorus photocatalysts were prepared via a solvothermal method for simultaneous organic dye degradation and hydrogen (H2) generation. The 5 wt% ZIF-8/RP photocatalyst achieved the highest H2 generation rate of 822.5 μmol h-1 g-1 and 92% rhodamine dye degradation under natural sunlight irradiation. This approach offers an effective strategy to replace costly and toxic traditional electron donors with organic dye pollutants for H2 generation.

Optimization of silicon solar cell design for use under concentrated solar irradiation

The task of reducing the cost of a unit of photoelectric-generated electricity is still relevant today. One of the most effective ways to do that is to use concentrator photovoltaic energy conversion systems with cheaper, small-area silicon solar cells (SC), because they require significantly less semiconductor material to make. In this study, the authors develop solutions to optimize the design and improve the manufacturing technology of silicon SCs of the combined diffusion-field type. Such SCs are used to concentrate solar irradiation. The authors propose design and technological solutions for the development and manufacture of a concentrator unit based on the Fresnel lens, which is designed to measure the photoelectric characteristics of SCs when concentrating solar irradiation. Next, the photoelectric characteristics of the combined diffusion-field type SCs were investigated under concentrated solar irradiation in natural sun conditions. The degree of concentration varied from 1X to 100X. Measuring the light I –V characteristics allowed determining photoelectric parameters of the cells — shortcircuit current, open-circuit voltage, fill factor and photoconversion efficiency. The obtained experimental results are in good agreement with the results of theoretical modeling. It is shown that due to the minimization of the specific series resistance, the samples of such SCs have high values of operational parameters in the range of natural solar irradiation concentration K=1X–100X.

Investigation on the compositional and performance evolution of cement paste subjected to Xenon radiation

This study addresses the critical question of how Xenon radiation, simulating natural solar radiation, affects the compositional, structural, and mechanical properties of cement paste. This aim is to understand the micro-to macro-scale changes in cement paste subjected to such radiation, a key concern for the durability of construction materials in solar-intensive environments. Employing a comprehensive suite of analytical techniques, including XRD, TG, 29Si NMR, 1H NMR, CT, SEM, and Vickers hardness testing, we systematically analyze the changes in phase composition, bound water content, silicate chain length in C–S–H, microstructure, and micro-mechanical behavior before and after radiation exposure. Our research uncovers a substantial decomposition of ettringite and a discernible reduction in the bound water content within the cement paste post-radiation exposure. Crucially, we detected a significant elongation in the C–S–H chain length, with a peak increase observed at 6%. This elongation is coupled with an increase in pore coarseness and a proliferation of internal defects. These alterations collectively lead to a marked decrease in the material's mechanical strengths: we noted a reduction in flexural strength by up to 18% and in compressive strength by as much as 25% at the macroscopic level. This research thus provides essential insights into the design and development of high-durability cementitious materials for solar radiation-intensive environments, contributing to the advancement of sustainable and resilient infrastructure.

Performance of a pool-type photoreactor operating in continuous mode under solar irradiation for the treatment of pollutants contained in wastewater

At present, there is no effective and sustainable treatment to remove organic micropollutants from wastewater. Solar photo-oxidation offers the possibility of a self-sustaining, energetically and ecologically compatible process based solely on the use of solar energy for treatment operations. The main scientific challenge is to operate a photoreactor in continuous mode using the solar resource, which is by nature discontinuous. To date, daily or monthly capacities have not been established. This study focuses on a photoreactor operating in continuous mode under natural solar irradiation conditions for the treatment of substances contained in wastewater. Two reactors of the flat panel and tubular type, as well as a new configuration of the pool type, were studied in order to identify the advantages and disadvantages of each reactor. The main focus of the study is on a continuously operating solar photoreactor for the treatment of wastewater containing a very wide range of substances. Using a global approach, the substances were classified according to their capacity to be degraded in order to highlight the conditions necessary to conduct a photo-oxidation treatment operation. The daily capacities and the efficiency of photo-oxidation carried out continuously under dynamic irradiation conditions were established.

Solar photocatalysis using post-consumer alkaline batteries for degrading contaminants of emerging concern in surface water

The goal of this study was to explore the use of post-consumer alkaline batteries' electrolytic paste as photocatalysts in solar processes for degrading contaminants of emerging concern (CECs) in surface water. Two types of alkaline batteries were used: Super Hyper UM-3SHSL8P6 (SH) and Alkaline LR6XAB/4B192 (AK), which were calcined at 500 °C for 4 h. The materials underwent various characterization tests, including SEM, XRF, BET, DRS, TGA, DRX, and pH at the Isoelectric Point (pI). The initial pH and catalysts dose conditions that result in the highest efficiency of methylene blue degradation were achieved through central composite design (CCD), i.e., 11.2, a dose of 1.5 g L−1 for AK and 1.6 g L−1 for SH. After 2 h of exposure to natural solar radiation, SH and AK achieved 72.6% and 96.6% removal efficiency in degrading the methylene blue model substance, respectively. This optimal condition was validated experimentally and statistically. In recycling tests, the photocatalysts maintained their efficiency until the third cycle with no statistically significant differences. The toxicity test with Lactuca sativa (lettuce) seeds showed that the treated water was not toxic. The AK catalyst was tested in the presence of three pharmaceutical drugs (ciprofloxacin, acetaminophen, and carbamazepine) in surface water at optimal pH 11.2 and natural pH (∼7), resulting in an overall removal of approximately 41.3% and 30.6%, respectively. Overall, our findings demonstrate that post-consumer alkaline batteries' electrolytic paste can be a viable option for solar heterogeneous photocatalysis under well-adjusted conditions.

Solar Photocatalytic Activity of Ba-Doped ZnO Nanoparticles: The Role of Surface Hydrophilicity.

Bare zinc oxide (ZnO) and Ba-doped ZnO (BZO) samples were prepared by using a simple precipitation method. The effects of Barium doping on the structural, morphological, and optoelectronic properties, as well as on the physico-chemical features of the surface were investigated and correlated with the observed photocatalytic activity under natural solar irradiation. The incorporation of Ba2+ ions into the ZnO structure increased the surface area by ca. 14 times and enhanced the hydrophilicity with respect to the bare sample, as demonstrated by infrared spectroscopy and contact angle measurements. The surface hydrophilicity was correlated with the enhanced defectivity of the doped sample, as indicated by X-ray diffraction, Raman, and fluorescence spectroscopies. The resulting higher affinity with water was, for the first time, invoked as an important factor justifying the superior photocatalytic performance of BZO compared to the undoped one, in addition to the slightly higher separation of the photoproduced pairs, an effect that has already been reported in literature. In particular, observed kinetic constants values of 8∙10-3 and 11.3∙10-3 min-1 were determined for the ZnO and BZO samples, respectively, by assuming first order kinetics. Importantly, Ba doping suppressed photocorrosion and increased the stability of the BZO sample under irradiation, making it a promising photocatalyst for the abatement of toxic species.

Exploring the scalability of solar-activated persulfate with iron-EDDS in raceway pond reactors for advanced wastewater treatment

In this study, the removal of microcontaminants (MCs) by the activation of persulfate (PS) with Fe(III)-EDDS under natural solar radiation in a low-cost raceway pond reactor (RPR) was investigated. The primary focus was to evaluate the effect of the Fe(III)-EDDS molar ratio, initial iron concentration, PS concentration, and initial pH on process performance while using sulfamethoxazole (SMX) and carbamazepine (CBZ) as model MCs. The investigation encompassed three different water matrices: natural water, synthetic municipal wastewater treatment plant (MWWTP) secondary effluent, and actual MWWTP secondary effluent. During experiments in natural water, it was found that 0.1 mM Fe(III) at a 1:2 molar ratio and 0.2 mM Fe(III) at a 1:1 molar ratio resulted in the most adequate operational conditions. Further experiments revealed a general decrease in process efficiency due to water matrix effects; however, this could be compensated by increasing the initial PS concentration and decreasing the initial operation pH. For example, the use of 0.2 mM Fe(III) at a 1:1 Fe(III):EDDS molar ratio, with 2 mM PS at pH 6, allowed for an 80% removal of the MCs sum in approximately 20 min, along with a significant decrease in chronic toxicity (Selenatrum Capricornutum) when working with actual waters. Nonetheless, the final experiment, focused on simultaneous MCs removal and wild bacteria inactivation in actual MWWTP secondary effluent, showed only a 1.6–1.8 log reduction of Escherichia coli, total coliforms, and Enterococcus faecalis. As such, further studies about the solar/Fe(III)-EDDS/PS process are needed to explore new strategies that improve its disinfection efficiency.

Near-infrared blocking window based on ATO-CWO/PVB nano-lamination

With the green developments of buildings, the next-generation windows are supposed to have excellent energy-saving behaviors, including thermal insulation and solar control. In this study, a novel ATO-CWO/PVB nano-laminated glazing with excellent NIR blocking ability was designed and fabricated. Such glazing has a good luminous transmittance at 63.2% while can block 94.5% of the whole NIR with wavelength between 780 and 2500 nm, which is far better than its counterparts such as ATO-based glazing, CWO-based glazing, metallic nanoparticle-based and metallic oxide nanoparticle-based glazing. In addition, the lamination design of ATO-CWO/PVB nanocomposite ensured its isolation from the air and can thus maintain long-term durability. Traditional CWO products would lose the NIR shielding ability within 3 months under the natural solar radiation, while the ATO-CWO/PVB nano-laminated glazing was demonstrated to maintain fairly stable optical properties in 5 months. Based on the nano-laminated glazing proposed in this study, a double-layered energy-efficient window was fabricated further, and outdoor experimental test was carried out to investigate its light/heat regulation performance, in comparison to the existing windows, including normal laminated glazing window and normal window. Results demonstrated that the newly developed energy-efficient window can achieve an indoor temperature decrease of 7.82 °C/6.64 °C, compared with double-layered clear window and double-layered normal laminated window, whereas it decreases the luminous level by about 37%/41% respectively. In order to further verify its energy-saving performance in hot regions, energy consumption simulation was conducted in Energy Plus software. Results showed the double-layered energy-efficient window can reduce the annual electricity consumption by 14%–18% in Hong Kong, compared with other tested windows.

Photocatalytic degradation and removal of type II pyrethroid pesticide (lambda-cyhalothrin) residue from wastewater using nanoceria for agricultural runoff application

Synthetic chemical pesticides' nature, mode of action, and persistence have brought about debates regarding whether the end justifies the means. Lambda-cyhalothrin is an important insecticide for farmers and households, with great accessibility and excellent action against pests and disease-carrying insects. Like other pyrethroid pesticides, Lambda-cyhalothrin targets the nervous system of insects or pests. However, its fate in the environment, especially in water and living systems, has made it crucial to explore methods of treating or degrading its residues in the environment. The present study aimed to develop a suitable method for the photocatalytic degradation and removal of Lambda-cyhalothrin (LCY) from wastewater and agricultural runoff. The nanoceria were used under natural solar irradiation without applying any scavenger chemical or buffer. This was synthesized using a simple co-precipitation method using cerium nitrate hexahydrate as a precursor. The synthesized nanoceria were characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared spectroscopy (FTIR) and particle size analysis. The average size of the particle was 27 nm. The photocatalytic degradation was conducted in batches with various pesticide concentrations exposed to different amounts of nanoceria. The initial and final concentrations of the LCY at each level were determined using Shimadzu UV spectroscopy. At optimum conditions, nanoceria was found to degrade and remove more than 63% of the initial pesticide concentration. This method can be suitable for degrading and removing pesticide residue from agricultural runoff (at source) and industrial effluents from synthetic pesticide industries.

Bismuth Tungstate Nanoplates-Vis Responsive Photocatalyst for Water Oxidation.

The development of visible-light-responsive (VLR) semiconductor materials for effective water oxidation is significant for a sustainable and better future. Among various candidates, bismuth tungstate (Bi2WO6; BWO) has attracted extensive attention because of many advantages, including efficient light-absorption ability, appropriate redox properties (for O2 generation), adjustable morphology, low cost, and profitable chemical and optical characteristics. Accordingly, a facile solvothermal method has been proposed in this study to synthesize two-dimensional (2D) BWO nanoplates after considering the optimal preparation conditions (solvothermal reaction time: 10-40 h). To find the key factors of photocatalytic performance, various methods and techniques were used for samples' characterization, including XRD, FE-SEM, STEM, TEM, HRTEM, BET-specific surface area measurements, UV/vis DRS, and PL spectroscopy, and photocatalytic activity was examined for water oxidation under UV and/or visible-light (vis) irradiation. Famous commercial photocatalyst-P25 was used as a reference sample. It was found that BWO crystals grew anisotropically along the {001} basal plane to form nanoplates, and all properties were controlled simultaneously by tuning the synthesis time. Interestingly, the most active sample (under both UV and vis), prepared during the 30 h solvothermal reaction at 433 K (BWO-30), was characterized by the smallest specific surface area and the largest crystals. Accordingly, it is proposed that improved crystallinity (which hindered charge carriers' recombination, as confirmed by PL), efficient photoabsorption (using the smallest bandgap), and 2D mesoporous structure are responsible for the best photocatalytic performance of the BWO-30 sample. This report shows for the first time that 2D mesoporous BWO nanoplates might be successfully prepared through a facile template-free solvothermal approach. All the above-mentioned advantages suggest that nanostructured BWO is a prospective candidate for photocatalytic applications under natural solar irradiation.

Ultrasonically assisted hydrothermal synthesis of tungsten(VI) oxide-TiO2 nanocomposites for enhanced photocatalytic degradation of non-narcotic drug paracetamol under natural solar light: insights into degradation pathway, mechanism, and toxicity assessment.

Photocatalytic degradation of pharmaceutical residues through natural solar radiation represents a green and economical treatment process. In this work, ultrasonically assisted hydrothermal synthesis of WO3-TiO2 nanocomposite was carried out at 140-150°C for 5h and calcinated at 600°C. The structural and optical properties of the synthesized material were investigated using techniques like XRD, FESEM/EDX, HRTEM, BET surface area, UV-DRS optical analysis, and photocurrent response. The band gap of TiO2 was successfully reduced from 3.0 to 2.54eV and thus making it effective under solar light. Complete degradation of paracetamol (50ppm and natural pH of 6.5) was achieved in 3.5h under natural sunlight at catalyst dose of 0.5g/l. The extent of mineralization was evaluated by measuring the COD reduction. Based on the degradation products identified by GC-MS/LC-TOF-MS, the degradation process under natural solar-light could be interpreted to initiate through OH. radical species. The toxicity removal of the treated paracetamol solution under natural solar-light was evaluated by the seed germination test using Spinacia oleracea seeds and exhibited 66.70% seed germination, confirming the reduction in toxicity. The enhanced photocatalytic efficiency of the nanocomposite is attributed to the higher surface area, low rutile content, lower band gap, and incorporation of WO3, which led to an extended absorption range and a slower rate of electron-hole recombination. The technical insights presented in this research offer a feasible approach for utilizing natural solar light driven photocatalysis for wastewater treatment in an efficient and sustainable way. The proposed degradation pathway, and seed germination test (toxicity removal) of the treated paracetamol solution under natural sunlight, has not been previously evaluated.

Photocatalytic generation of H2 by photoreforming of organics in aqueous suspension of Nb2O5/C3N4 composites

Bare and composite materials based on C3N4 and Nb2O5 have been used as photocatalysts for the photoreforming of aqueous solutions of oxygenated compounds. Both Nb2O5 and Nb2O5/C3N4 composites have been prepared by hydrothermal synthesis and all of them were physical-chemically characterized. In this work two different carbon nitride species i.e. graphitic (g-C3N4) or thermo-etched (TE-C3N4) were used both alone or coupled with Nb2O5. The photo-reforming activity has been measured under UV irradiation by using the semiconductors in the presence of Pt as co-catalysts and, in the case of the best material, it was, for the first time, measured and compared also under natural solar irradiation. It was found that the highest activity was achieved with the Nb2O5/TE-C3N4 10:1–200 photocatalyst for which the hydrogen formation under UV irradiation resulted of ca. 46 mmol·h-1·g-1 with an apparent quantum yield of ca. 14 %. The maximum solar hydrogen productivity was 1.8 mmol·kJ-1·g-1 or 0.81 mmol·h-1·g-1.

Gold-reduced graphene oxide intimated BiVO4–ZnO mixed oxide composite with leveraged charge carrier transport under solar radiation

In a desire to enhance the photocatalytic activity of the BiVO4–ZnO mixed oxide, the mixed oxide has been encapsulated with gold decorated reduced graphene oxide (Au-rGO) using tetra-n-butylammonium bromide. The Au-rGO/BiVO4–ZnO hybrid composite was characterized for its physicochemical properties. The microscopic images of the composite from HR-TEM studies showed the aggregated spherical morphology of the particles. The images also revealed the intimation of two-dimensional Au-rGO layer over the BiVO4–ZnO mixed oxide surface. X-ray diffraction studies confirm the formation of the composite with the presence of characteristics diffraction pattern for BiVO4–ZnO and Au- rGO. The nature of diffraction peaks also revealed the size reduction of crystallite particles of the composite after inclusion of BiVO4 in the parent ZnO. The optical properties of the prepared materials were deduced using DRS-UV-visible spectroscopic studies and photoluminescence studies. The Tauc plots for ZnO, BiVO4–ZnO and Au-rGO/BiVO4–ZnO showed their optical band gap to be 3.3, 2.8 and 2.9 eV respectively. The emission intensity in photoluminescence spectra revealed the charge carrier recombination order as ZnO > BiVO4–ZnO > Au-rGO/BiVO4–ZnO. The Au-rGO/BiVO4–ZnO composite was employed as photocatalyst in the degradation methylene blue dye under natural solar radiation. The degradation experiment was also repeated with bare ZnO and BiVO4–ZnO mixed oxide. The results revealed the enhanced photocatalytic activity of the Au-rGO/BiVO4–ZnO composite. The rate constant for the degradation reaction with the three catalyst viz., ZnO, BiVO4–ZnO and Au-rGO/BiVO4–ZnO were found to be 2.61 × 10−2 min−1, 3.04 × 10−2 min−1 and 3.96 × 10−2 min−1 respectively.

Photocatalytic Degradation of Pharmaceutical Trimethoprim in Aqueous Solution over Nanostructured TiO2 Film Irradiated with Simulated Solar Radiation

Pharmaceuticals are characterized by a wide range of physical, chemical, and biological properties and functionalities that contribute to their inherent complexity as compounds. Unfortunately, human carelessness during the production, use, and disposal of these compounds results in their presence in the environment. This study utilized a nanostructured TiO2 film on a glass ring at the bottom of a reactor and simulated a solar radiation lamp as the radiation source for both photocatalytic and photolytic experiments, with the aim of unraveling the mechanism behind the degradation of trimethoprim (TMP), a pharmaceutical compound. This approach provides a novel perspective on the role of TiO2 in the degradation of pharmaceuticals and could pave the way for more efficient and sustainable wastewater treatment methods. Scavenger studies were carried out using isopropanol, ammonium oxalate, and triethanolamine to examine the photocatalytic mechanism. Isopropanol and triethanolamine were found to impede the photocatalytic degradation of TMP, highlighting the significance of hydroxyl radicals and positive holes in the degradation process, while no inhibition was observed in the presence of ammonium oxalate. The complete degradation of TMP through photocatalysis under simulated solar radiation was observed in ultra-pure water in fewer than 3 h, as indicated by the results. Our findings suggest that utilizing natural solar radiation as a source of UV-A radiation in reactor configurations based on this approach holds promise for cost-effective pharmaceutical degradation treatment in wastewater treatment plants. The practical potential of this approach is supported by the results obtained under simulated solar radiation with an irradiation intensity in the UV-A region of 33 ± 2 W/m2.